Doctor blades have been used for years in various different applications. Typically, a doctor blade is used to help separate a material from a piece of equipment. For example, a doctor blade may be used to help remove a web of material from a drum or plate to which the material has been attached. Doctor blades may also be used to clean equipment and/or to impart one or more characteristics into the product being manufactured by the equipment.
In the paper industry, for example, doctor blades are often used to help remove the paper web from a drying drum, such as, for example, a Yankee dryer, to which the paper web is adhered. In certain papermaking processes, the doctor blade that removes the paper web from the drying drum or any other drum may also be used to crepe the paper to some degree. Such doctor blades are often referred to as “creping blades”. The present invention is directed to creping blades, and more particularly to creping blades used in papermaking and other web making processes.
The geometry of the creping blade and the particular set-up configuration of the creping blade with respect to the equipment with which it interacts can provide for variations in the way the creping blade performs its intended function. For example, it is known that the bevel or angle on the blade can affect the blades performance and/or the physical characteristics of the material being removed by the blade. Further, it is known that the location of the blade against the equipment with which it is intended to interact and the angle of the blade to that equipment can also provide for variations in the performance of the manufacturing process as well as the physical characteristics of the material being removed by the blade.
Despite the vast amount of information available relating to the bevel or angle of the doctor blade and/or the set-up configuration of such blades for different machine processes, there is still a need to improve the performance of creping blades and to provide creping blades that can uniquely affect the physical attributes of the materials with which they interact. Due to the way that a creping blade is typically used in the web making process (the web is removed from a drying roll at high speed by impacting the web against the creping blade), the creping blade can and does often cause problems with throughput, tearing of the web, reducing the strength of the web, generating dust, etc.
The present invention provides improved creping blades that address individually and/or together many of the problems presented by currently available creping blades. Specifically, it has been newly discovered that the geometry of the trailing edge or “heel” of the creping blade (the edge not positioned against or toward the piece of equipment with which the blade interacts) can be modified to provide unique benefits to the processes and/or materials with which the creping blade interacts. More specifically, it has been found that modifying the edge break at the heel of the blade can provide for improved machine performance, such as, for example, line speed increases, an increase in line reliability, an improvement in sheet stability, a reduction in the amount of dust or other material derived from the web interacting with the blade and/or can provide the product being manufactured with unique physical attributes not easily attainable by using the doctor blades that are currently commercially available. Further, the blades of the present invention can provide a less traumatic interaction with the paper web, which can help reduce the amount of material needed to form a particular end product in certain circumstances and/or allow for the use of less expensive materials to produce the desired end product.